Description
Description: Institut für Geowissenschaften, University of Kiel, Olshausenstr. 40, 24098 Kiel, Germany. Ice core records demonstrate a glacial-interglacial atmospheric
CO2 increase of ~ 100 ppm. A transfer of
~ 530 Gt C is required to produce the deglacial rise of
carbon in the atmosphere and terrestrial biosphere. This amount is
usually ascribed to oceanic carbon release, although the actual
mechanisms remained elusive, since an adequately old and
carbon-enriched deep-ocean reservoir seemed unlikely. Here we
present a new, though still fragmentary, ocean-wide 14C
dataset showing that during the Last Glacial Maximum (LGM) and
Heinrich Stadial 1 (HS-1) the 14C age difference between
ocean deep waters and the atmosphere exceeded the modern values by
up to 1500 14C yr, in the extreme reaching
5100 yr. Below 2000 m depth the 14C ventilation
age of modern ocean waters is directly linked to the concentration
of dissolved inorganic carbon (DIC). We assume that the range of
regression slopes of DIC vs. Δ14C remained constant
for LGM times, which implies that an average LGM aging by
~ 600 14C yr corresponded to a global rise by
~ 85–115 Μmol DIC kg−1 in the deep ocean. Thus, the
prolonged residence time of ocean deep waters indeed made it
possible to absorb an additional ~ 730–980 Gt DIC,
~ 1/3 of which transferred from intermediate waters. We infer
that LGM deep-water O2 dropped to suboxic values of <
10 Μmol kg−1 in the Atlantic sector of the Southern ocean,
possibly also in the subpolar North Pacific. The transfer of aged
deep-ocean carbon to the atmosphere and the ocean-atmosphere
exchange are sufficient to account for the 190-‰
drop in atmospheric 14C during the so-called HS-1
Mystery Interval.